Theoretical Nuclear Physics (SH2011, Second cycle, 6.0cr/ SH3311, - - PowerPoint PPT Presentation

Theoretical Nuclear Physics

(SH2011, Second cycle, 6.0cr/ SH3311, Third cycle, 7.5cr) (March 23, 2017)

Comments and correc-ons are welcome! Chong Qi, chongq@kth.se https://www.kth.se/social/course/SH2011/

The course contains 12 sec0ons

² Basic Quantum Mechanics concepts ² Basic nuclear physics concepts: Pairing, single-particle excitations, square well ² Single-particle model and the spin-orbit interaction ² Magnetic resonances in nuclei ² Nuclear deformation and the Nilsson model, the cranking approximation ² Two-particle system, LS and jj coupling ² Modern theory of the nuclear force, isospin symmtry ² Seniority coupling scheme and neutron-proton coupling scheme ² Second quantization ² Hartree-Fock and energy density functional ² Tamm-Dankoff & Random Phase Approximations ² One-nucleon operators, gamma and beta decays, 14C-dating β decay ² Many-body operators and alpha decay ² If time allows, we may also cover: ² Scattering theory and resonances ² Continuum, nuclear halo and astrophysics

• K. Heyde, Basic ideas and concepts in nuclear physics, IOP Publishing 1994
• K. Heyde, The nuclear shell model, Springer-Verlag 2004
• P. J. BRUSSAARD and P. W. M. GLAODEMANS, SHELL -MODEL APPLICATIONS IN NUCLEAR

SPECTROSCOPY North-Holland 1977 G.F. Bertsch, Practitioner's Shell Model (North-Holland, New York, 1972)

• J. Suhonen, From Nucleons to Nucleus: Concepts of Microscopic Nuclear Theory, Springer, Berlin, 2007

D.J Rowe & J.L. Wood, FUNDAMENTALS OF NUCLEAR MODELS, World Scientific, 2010

• R. D. Lawson, Theory of the nuclear shell model, Clarendon Press, 1980
• I. Talmi, Simple Models of Complex Nuclei (Harwood Academic, Reading, UK, 1993), Chap. 1-13

S.G. Nilsson and I. Ragnarsson: Shapes and Shells in Nuclear Structure, Cambridge Press, 1995

• P. Ring and P. Schuck, The Nuclear Many-Body Problem (Springer-Verlag, New York

1980). Bohr.A,.Mottelson,B. Nuclear.Structure.Vol.I&II.World.Scientific,.1998 Physical Review C http://prc.aps.org/ Physical Review Letters http://prl.aps.org/ Nuclear Physics A http://www.sciencedirect.com/science/journal/03759474 Journal of Physics G, http://iopscience.iop.org/0954-3899 European Physical Journal A, http://www.springerlink.com/content/1434-6001 http://arxiv.org/archive/nucl-th

References:

There will be no Final Exam for this course.

• Home works (11 in total): Pre-reading + exercises
• projects (note + oral presentation)
• Finish the exercises and hand in (two copies) in due time.
• Read the lecture notes in advance

Ø Pay special attention to the key concepts I mentioned at the beginning of each chapter

• Choose one or several projects to work with

Before the lecture During the lecture

• Present your the exercises
• Mark and approve one copy of the others’
• Present your projects
• Group discussion on key concepts

After the lecture and before you go: Write on a small piece of paper and leave it to me

• The hard/muddy point
• The interesting point

Bases of your assessment. To pass,

• ne should have

>7 Approved homeworks >1 Approved projects Higher requirement for PhD and late submission

The (Quantum) Ladder

Molecules Atoms Nuclei Super- strings ? Cells, Crystals, Materials Living Organisms, Man-made Structures

???

Baryons, mesons Elementary Particles Quarks and Leptons

subatomic macroscopic

Stars Planets Galaxy clusters Galaxies

Mesoscopic

Atomic Physics

The physics of the electronic, extra-nuclear structure of atoms

Nuclear Physics

The physics of the atomic nucleus, believed to be constituted

• f neutrons and protons

Elementary Particle Physics

The physics of quarks and gluons, believed to be the constituents of protons and neutrons, and of leptons and gauge bosons and… who knows what else! Quarks, gluons, leptons, and gauge bosons are believed to have no substructure.

Group activity 1: Who has taken the Nuclear Physics course? Quantum Physics (Second quantization)?

1896: Discovery of radioactivity (Becquerel) 1911: Discovery of the nucleus (Rutherford experiment) 1932: Discovery of the neutron (Chadwick) 1935: Bethe-Weiszaker mass formula 1939: Discovery of (neutron-induced) fission 1949: Shell model (Goeppert-Mayer, Jensens) 1951: Collective model (Bohr, Mottelson, Rainwater) 1957: Nuclear superfluidity (Bohr, Mottelson) Since then: Nuclear forces, many-body methods (HF, HFB, RPA, GCM, Green function, etc. Group activity 2: Tell something about your knowledge on (theoretical) nuclear physics and what you want to know?

The nuclear constituents

Notation used to represent a given nuclide

N A Z X

Z: atomic number A: atomic mass number N: neutron number X: chemical symbol

H

M M × ≈ integer

M: the mass of a specific atom MH: the mass of a hydrogen atom

N Z A + =

Nomenclature Nuclide A specific nuclear species, with a given proton number

Z and neutron number N

Isotopes Nuclides of same Z and different N Isotones Nuclides of same N and different Z Isobars Nuclides of same mass number A (A = Z + N) Isomer Nuclide in an excited state with a measurable half-life Nucleon Neutron or proton Mesons Particles of mass between the electron mass (m0) and

the proton mass (MH). The best-known mesons are π mesons (≈ 270 m0), which play an important role in nuclear forces, and µ mesons (207 m0) which are important in cosmic-ray phenomena

Strangeness degree of freedom

hyperon is any baryon containing one or more strange quarks, but no charm, bottom, or top quark. Λ0 → p+ + e− + νe Λ0 → p+ + µ− + νµ https://en.wikipedia.org/wiki/Hyperon

Natural unit

Nuclear masses ~ 10-27 kg

Atomic Scale ~ eV Nuclear Scale ~ MeV (106 eV) Particle Scale ~ GeV (109 eV)

J 10 1.602 eV 1

• 19

× =

Convenient energy units

What is the mass of a nucleon?

• 1MeV
• 1GeV

• Atomic radius of aluminum = 1.3 x 10-10 m

Nuclear radius aluminum = 3.6 x 10-15 m

Size of Nuclei What is the size of the nucleus

• nanometer
• femtometer
• picometer

The convenient unit for measuring the nuclear mass : is called the atomic mass unit or for short amu.

u

The mass of a 12C atom (including all six electrons) is defined as 12 amu (or 12 u) exact.

1 u =1 amu =1.6605402 (10)×10−27 kg = 931.49432 (28) MeV/c2

The mass of a proton

2

MeV/c 27231 . 938 ) 12 ( 007276470 . 1 = = u M p

The mass of a neutron

2

MeV/c 56563 . 939 ) 12 ( 008664898 . 1 = = u M n

(1)

Total binding energy B(A,Z)

2

c )] , ( [ ) , ( Z A M NM ZM Z A B

n p

− + =

Definition: The total binding energy B(A,Z) is defined as the total minimum work that an external agent must do to disintegrate the whole nucleus completely. By doing so the nucleus would no longer be existent but disintegrated into separated nucleons. This can also be considered as the total amount of energy released when nucleons, with zero kinetic energy initially, come close enough together to form a stable nucleus.

A Z A B Z A Bave ) , ( ) , (

.

=

An interesting measured quantity is the averaged binding energy per nucleon (2) (3)

How large is nuclear binding energy per nucleon?

• 1MeV
• 10MeV

The average binding energy per nucleon versus mass number A Bave = B/A

nucleus bound tightly most the is and energy binding nucleon per MeV 8.8 has Fe

56 26

Anything else one can learn from this?

The binding energy of a nucleus

2

c )] , ( [ ) , ( Z A M NM ZM Z A B

n p

− + =

(9) Definition: From the liquid drop model ̶ Weizsäcker’s formula Carl Friedrich von Weizsäcker, 1993 A German physicist (1912-2007)

η δ + ± − − − − = A Z N a A Z a A a A a Z A B

A C S V 2 3 / 1 2 3 / 2

) ( ) , (

(10)

Separation energy (S) (1). The separation energy of a neutron Sn

n X X

N A Z N A Z

+ →

− − 1 1

2

c )] , ( ) , 1 ( [ Z A M M Z A M S

n n

− + − =

(4)

) , ( c ) ( c ) , (

2 2

Z A B NM ZM Z A M

n p

− + =

) , 1 ( c ] ) 1 ( [ c ) , 1 (

2 2

Z A B M N ZM Z A M

n p

− − − + = − ) , 1 ( ) , ( )} , ( c c ) , 1 ( c ] ) 1 ( {[

2 2 2

Z A B Z A B Z A B ) NM ZM

• (

M Z A B M N ZM S

n p n n p n

− − = + + + − − − + =

) , 1 ( ) , ( Z A B Z A B Sn − − =

(5)

Separation energy (S) (2). The separation energy of a proton Sp

) 1 , 1 ( ) , ( − − − = Z A B Z A B S p

(6)

p Y X

N A Z N A Z

+ → −

− 1 1

(3). The separation energy of a α-particle Sα 2 4 2 2 4 2

He + →

− − − N A Z N A Z

Y X

Sα = B(A, Z)− B(A − 4, Z − 2)− B(4,2)

(7)

The naturally occurring nuclei

Total Angular momentum and Nuclear spin For nuclei: The nucleus is an isolated system and so often acts like a single entity with has a well defined total angular momentum. It is common practice to represent this total angular momentum of a nucleus by the symbol I and to call it nuclear spin. [Associated with each nuclear spin is a nuclear magnetic moment which produces magnetic interactions with its environment.] For electrons in atoms: For electrons in atoms we make a clear distinction between electron spin and electron orbital angular momentum and then combine them to give the total angular momentum.

What is spin of the ground state of an even-even nucleus?

• Zero
• Non-zero

Why?

In a non-rela-vis-c approxima-on, nuclear proper-es are described by the Schrödinger equa-on for A nucleons Ψ(1,2, . . . ,A) denotes an A-body wave func-on. The Hamiltonian H contains nucleon kine-c energy operators and interac-ons between nucleons (two-body and three body). i denotes all relevant coordinates of a given par-cle (i = 1,2, . . . ,A).

Prac0cally it is formidable!!

The full Hamiltonian

Basic notions of quantum mechanics

• Wave function encodes all information about a quantum system
• Schrödinger equation gives the wave-function
• Energy of the system, and its evolution in time is dictated by the Hamiltonian,
• Hamiltonian spectrum (eigenvalues of operator) can be

– Discrete: bound-states, localized – Continuous: continuum, resonance, delocalized scattering states

• To an observable (measurable) quantity corresponds a Hermitian operator

A hermitian operator has then and only then a complete system of Eigenfunctions, if it is self-adjoint.

6j symbol

9j symbol